Thermodynamic properties of carbon dioxide clusters by M06-2X and dispersion-corrected B2PLYP-D theory

The M06-2X and B2PLYP-D functionals have been applied to predict structures and energies for (CO2)n clusters up to n = 16. A comparison between M06-2X, B2PLYP-D and benchmark CCSD(T) results indicates that M06-2X is capable of providing accurate binding energies. Stepwise M06-2X (CO2)n clustering free energies exhibit a sharp discontinuity at the magic cluster size n = 13 and systematically shift to more exergonic values with decreasing temperature, in particular for larger clusters. These results indicate that the M06-2X method provides an accurate and cost effective description of non-covalent interactions in (CO2)n clusters and therefore may provide important information on CO2 nucleation phenomena.